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CAP200 Managing Database

Homework1DOA: 23/08/10DOS:6/09/10

Homework Title / No. : ________1__________________Course Code : _CAP200_____

Course Instructor : ___Anjlee _Verma____________ Course Tutor (if applicable) : ____________

Date of Allotment : _23/08/2010__________ Date of submission : ____6/09/2010_________

Students Roll No.___D3801A09______________ Section No. : _____D3801_________

Declaration:

I declare that this assignment is my individual work. I have not copied from any other students work or

from any other source except where due acknowledgment is made explicitly in the text, nor has any part

been written for me by another person.

Students Signature : __Himanshu Gautam__

Evaluators comments:

_____________________________________________________________________

Marks obtained : ___________ out of ______________________

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Part A

Q1. Properties satisfied by a transaction for a transfer of funds from one

bank account to another. Evaluate.

Answer:- A money or value transfer service may be provided by persons (natural or legal)

formally through the regulated financial system or informally through non-bank financialinstitutions or other business entities or any other mechanism either through the regulated

financial system (for example, use of bank accounts) or through a network or mechanism that

operates outside the regulated system. In some jurisdictions, informal systems are frequently

referred to as alternative remittance services or underground (or parallel) banking systems. Often

these systems have ties to particular geographic regions and are therefore described using a

variety of specific terms. Some examples of these terms include hawala, hundi, fei-chien, and the

black market peso exchange.

Q2. Design a small application on student management system for the

purpose of enquiry; we will use any database system to store persistent

data.

Answer:-

create table Student

(

Name varchar(20),

Reg_No int primary key,

Roll_No int,

Section varchar(10),

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Program_Code int,

Program_Name varchar(30),

Fee varchar(20),

Address varchar(50)

)

insert into Student values('Himanshu',108,9,'272',140,'BCA-

MCA','25000','Ludhiana')

insert into Student values('Anuj',118,10,'271',140,'BCA-

MCA','25000','Ludhiana')

insert into Student values('Nandu',180,22,'270',140,'BCA-MCA','25000','Kolkata')

NAME RE G_ NO ROLL_NO SECTION PROGRAM_CODE P RO GRAM_NAME FEE AD

Himanshu 108 9 272 140 BCA-MCA 25000 Ludh

Anuj 118 10 271 140 BCA-MCA 25000 Ludh

Nandu 180 22 270 140 BCA-MCA 25000 Kolka

3 rows returned in 0.01seconds

Q3. We have a problem that would arise if the responsibilities were notdischarged. For this problem list five responsibilities of a database

management system.

Ansewer:-

a) Efficient data manipulation. A DBMS should make manipulation of its contents

(e.g., through relational joins) more efficient by indexing records. If it implements relational

operations in a nave way, the worst-case running time proportional to the product of the sizes

of the relations could be many times slower than that of an efficient implementation. Given the

current sizes of large databases (millions to billions of records), this could mean a factor ofhundreds to thousands.

b) Consistency. A DBMS must update its contents in a safe way to reflect the results of

possibly concurrent transactions. If concurrent transactions are not conducted in a way such that

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updates are noninterferent (as well as integral) then harmful effects such as invalid values can

occur.

c) Security and Isolation. A DBMS should ensure that only authorized reads and writesoccur with respect to its contents. Views should protect private information, malicious changes

(data diddling) should be prevented, and unauthorized processes should not be able to access and

transmit protected information stored within the database. If this is not done for databases with

sensitive information, then serious breaches of security at private, local, national, or international

level may occur.

d) Integrity and Durability. A DBMS should ensure that fields of records in different

parts of the database are consistent. In particular, it can be used to ensure referential integrity,

i.e., that values that appear in one relation for a given set of attributes also appear for another set

of attributes in another relation (Section 4.2.5 Silberschatz et al. 5e, p. 129 132). Without

integrity constraints, updates can happen that can cause erroneous conditions: overdrafts on

financial accounts at banks and departments, for example. The results should also persist, or the

user cannot be assured of the reliability of confirmation messages.

e) Back up and Recovery Services. It includes the following responsibilities: provide

database backup/recovery services, provide off-site tape storage services, provide optional

operational recovery services.

Part B

Q4. Give at least two reasons why database system support data

manipulation using a declarative query language such as SQL, instead

of just providing a library of C or C++ functions to carry out data

manipulation.

Answer:-

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a)Representation Independence and Transparency (Strong Typing). A DML lets

the programmer manipulate relations as first-class data structures, decreasing the chance of low-

level mistakes by hiding details of how relations are represented and transformed.

b) Efficiency. It may be more efficient to perform certain operations such as relational

joins using sort arrays and hash tables instead of iterator patterns and functions. The database

itself can keep the sequential storage records needed for bookkeeping.

Q5. Consider a table Customer (cidPK, cname, city, rating)

Write SQL queries to compute the average rating using AVG(rating);

the sum of the ratings using SUM(rating); and the number of ratingsusing COUNT(*).

If you divide the sum computed above by the count, would the result be

same as AVG? Justify your answer.

Answer:-

create table Customer

(

C_ID primary key,

C_Name,

City varchar(20),Rating int

)

insert into Customer values(1,'Himanshu','Ludhinan',5)

insert into customer values(2,'Rajni','Ludhiana',3)

insert into customer values(3,'Anuj','Ludhiana',4)

insert into customer values(4,'Karan','Ludhiana',5)

select * from customer

select Sum(RATING) from

customer

C_ID C_NAME CITY RATING

3 Anuj Ludhiana 4

4 Karan Ludhiana 5

1 Himanshu Ludhiana 5

2 Rajni Ludhiana 3

4 rows returned in 0.00 seconds

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select AVG(Rating) from customer

select Count(Rating) from customer

When we divide the sum computed

above by the Count the result is same as AVG as follows:-

select (SUM(Rating)/COUNT(Rating)) from Customer

Q6. Adopting database administration

concepts can improve an organizations effectiveness, since a focal point isestablished for the responsibility, the management, and the control of the total

data resources. Give some of the advantages to management of having a

strong database administration function.

Answer:-

a) Data Definition. A DBA designs the basic schema and implements it by using a data

definition language (DDL) or data definition user interface to create tables.

b) Initial storage structure design. A DBA translates the initial schema design (e.g.,

star/constellation, data warehouse) into a storage design by specifying where tables actually

reside and what kind of indexing information is needed for the specified organization. Examples

include data dictionaries and multilevel indices .

S UM( RATING )

17


AV G ( RATING )

4.25


CO UNT( RATING )

4


( S UM( RATING ) /CO UNT( RATING ) )

4.25


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c) Updating and changing schemas. A DBA maintains the schema, adding or dropping

fields to reflect reorganization of the database, refactoring it into different tables when needed,

and changing the actual physical organization of tables.

d) Administering access privileges. A DBA defines, grants and revokes privileges for

accessing tables, either directly or by means of views.

e) Backups, restores, and performance tuning. A DBA administers regular

incremental backups of database contents, storage quotas, and restoration of data corrupted or

lost in crashes. He or she may also look at usage statistics in order to decide on an acceptable

use policy (CPU quotas) and perform basic load balancing.

cap200 d3801a09

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